Hot gas engine

ABSTRACT

A hot gas engine having a buffer space, a working space in communication with a medium supply duct including a controllable inlet valve, a medium outlet duct including a controllable exhaust cock, a communication duct including a bypass valve between the working space and buffer space, a first control device which is movable against the action of a spring for operating the inlet and exhaust valves, and a second control device which is movable against the action of the spring for operating the bypass valve, the control devices being constructed so that during normal operation a movement of the second control device is associated with the same movement of the first control device, while upon braking with the engine the bypass valve is maximally opened and by moving the first control device only the inlet cock can be opened to provide a maximum braking torque.

United States Patent 1 3,600,886

[72] inventors Hendrik Alphons .laspers; Primary ExaminerMartin P.Schwadron Gregorlus Theodorus Marla Neelen, both of AssistantExaminer-A. M. Zupcic Emmasingel, Eindhoven, Netherland Alromey Frank R.Trifari [2i App]. No. 855,170

22; Filed Sept. 4, 1969 [45] Patented Aug. 24, 1971 [73] Assignee U.S.Philips Corporation 32 1 Priority ABSTRACT: A hot gas engine having abuffer space, a work- I I ing space in communication with a mediumsupply duct in- [33] N cluding a controllable inlet valve, a mediumoutlet duct in- [N M2816 cluding a controllable exhaust cock, acommunication duct including a bypass valve between the working spaceand buffer [54] HOT GAS ENGINE space, a first control device which ismovable against the acu Cum 4 Dn'tng Ft tion of a spring for operatingthe inlet and exhaust valves, and

a second control device which is movable against the action of [52] US.Cl. 60/24, 62/6 the spring for operating the bypass vahe the controldevices [51] CL 9/00 being constructed so that during normal operation amovel Field snub 60/24; 62/6 ment of the second control device isassociated with the same movement of the first control device, whileupon braking with [56] References the engine the bypass valve ismaximally opened and by mov- UNITED STATES PATENTS ing the first controldevice only the inlet cock can be opened 3,466,867 9/1969 Brandes 60/24to provide a maximum braking torque.

, 5 N -11" .l]I'- r n v A 2 27 28 I 12| I 1. as 31. 3s 33 23 PATENTED mmm.

SHKET 1 OF 3 INVENTORS HENDRIK A. PERS GREGORIUS M.NEELEN BY AGEN 1 1one INVENTORS HENDRIK AJASPERS GREGORIUS T. M.NEELEN PATENTEU M1824 l9?!SHEET .3 OF 3 INVENTORS HENDRIK A. JASPERS GREGORIUS T- M.NEELEN BY AAGENT HOT GAS ENGINE The invention relates to a hot gas enginecomprising one or more working spaces each of which communicates, ifdesirable through a nonreturn valve permitting flow in the direction ofthe respective working space, with a medium inlet duct comprising acontrollable suppletion or inlet cock and in which furthermore eachworking space communicates if desirable through a nonreturn valveopposing flow of medium in the direction of the respective workingspace, with a medium outlet duct, the removal of medium through saidduct being controlled by a controllable exhaust cock and furthermoreeither a communication duct being provided between each working spaceand a buffer space containing the same medium as the working space, or acommunication duct is present between the medium inlet and medium outletduct, a bypass-closing member being present in said communicationduct(s) which is continuously controllable between its closed positionand its fully open position.

It is known to control the supplied power of hot gas engines by varyingthe average pressure in the working space. Increase of the suppliedtorque is achieved by temporarily opening the suppletion or inlet cockin the medium supply duct as a result of which working medium flows froma storage container into the working space(s) of the engine and theaverage pressure level increases. On the other hand, reduction of thetorque supplied by the engine can be achieved by temporarily opening theexhaust cock, as a result of which working medium is pumped back fromthe working space to the storage container, for example, by means of acompressor. Since for structural reasons the dimensions of thecompressor may not be unduly large, the removal of working medium willoccur only comparatively slowly. A rapid reduction of torque can beobtained by opening, in addition to the exhaust cock, a bypass valve ina communication duct between the working space and a buffer space inwhich the same medium is present as in the working space or in acommunication duct between the medium inlet and medium outlet duct. As aresult of this such a distortion of the pressure-volume diagram isobtained that a rapid reduction of the supplied torque occurs. This isbased on the fact that due to the flow losses occurring in the bypassvalve the phase difference between the volume and pressure variationsoccurring in the cold and warm spaces, respectively, of the enginebegins to deviate from the optimum phase difference, in the case of asmall opening of the bypass valve the torque will decrease, it is true,but remains positive so that the engine still supplies power. When thebypass valve is further opened, the torque will become zero, and when itis still further opened it will even become negative so that the enginecan absorb power. in a given position of the bypass valve a maximumnegative torque is obtained and upon further opening the negative torquedecreases again. When the present hot gas engine is applied for tractionpurposes, braking with the engine can be effected consequently by meansof the bypass valve. The value of the braking torque supplied by theengine depends upon the pressure in the engine and upon the number ofrevolutions, in addition to the position which the bypass valve assumes.Accordingly, as the pressure is higher, the supplied barking torque willbe larger.

ln known hot gas engines of the type to which the present inventionrelates, a power control device is present with which on the one handthe inlet cock can be opened and on the other hand the exhaust cock canbe set to its exhaust position and simultaneously the bypass valve canbe opened. Through the exhaust the medium is removed from the workingspace(s) and upon reaching the desired pressure (required power), boththe exhaust and the bypass cock are closed. This means that a highbraking torque cannot be supplied by the engine for a longer period oftime.

It is the object of the invention to provide a hot gas engine comprisinga control device with which the inlet exhaust and bypass cocks can beoperated so that for a long period of time, for example, when a vehicledrives down a slope, a high braking torque can be supplied.

In order to achieve the object of this invention, the hot gas engine hasa first control device which is movable against the action of a springfor controlling the inlet and exhaust cocks and which, upon movementagainst the action of the spring, brings the inlet cock in its openposition and, uponmovement in the direction of the action of the spring,bringstheexhaust cock in its exhaust position; said movement in thedirection of spring action being restricted by a first fixed stopmember. The engine furthermore comprises a second control device whichis likewise movable against the action of a spring for controlling thebypass valve, which control device, upon movement against the action ofthe spring, closes the bypass valve or moves it to its closed positionand, upon movement in the direction of the action of the spring, opensitor opens it further, the movement of said second control device in thedirection of the action of the spring being limited by a second stopmember. Each of the two control devices is coupled to apressure-sensitive element which, dependent upon the pressure in theworking space(s) of the engine, assumes a given position in such mannerthat when the pressure in the working space(s) increases or decreases,the adjustment .of the two control devices varies in that sense that theinlet cock moves to its closed position and the exhaust cock moves toits nonexhaust position, respectively, and the bypass valve moves to itsclosed position. The first and the second stop members are arranged sothat the distance over which the first control device is movable in thedirection of the action of the spring, is smaller than the distance overwhich the second control device is movable in that direction, The enginefurthermore comprises an element which is sensitive to the number ofrevolutions; when the number of revolutions, reduces below a zero loadnumber of revolutions this element may be adjustable. To move the secondcontrol device away from the second stop member, the second controldevice being constructed so that in a position of the two controldevices in which the bypass valve is closed and the inlet and exhaustcock both assume their closed and nonexhaust position, respectively, amovement of the second control device also results in an equally largemovement of the first control device.

During normal operation of the hot gas engine according to the inventionthe inlet cock can be opened upon movement against the action of thespring by moving the second control device with which simultaneously thefirst control device is.

also moved. As result of this medium will flow to the working space(s)of the engine through the medium supply duct. As a result of this thepressure in said working space(s) will increase so that thepressure-sensitive element experiences a displacement in that sense thatthe ,control devices experience a movement opposite to the initialmovement so that the inlet cock is closed. The same, but then in thereverse direction, occurs upon moving the control devices in thedirection of the action of the spring, the first control device againfollowing the second. In this manner a given pressure level in theworking space(s) is reached that is associated with any position of thecontrol devices. So a given power supplied by the engine is associatedwith any position of the control devices, so that said control devicesare comparable to the accelerator of internal combustion engines. Whenthe two control devices are entirely released, a movement of the firstcontrol device takes place until it engages the stop member, the secondcontrol device experiencing a slightly larger displacement until itengages the second stop member. The exhaust valve then is in its exhaustposition and the bypass valve is maximally opened, that is to say, theengine supplies a maximum braking torque. Medium is now conducted awayfrom the working space(s) through the outlet duct, so that the pressuretherein decreases as a result of which the pressure-sensitive elementexperiences a displacement, thereby also moving the control devices. Dueto this movement the exhaust cock moves to its nonexhaust or closedposition and the bypass valve moves to its closed position. As a resultof the unequal arrangement of the stop members the bypass-closing memberwill not reach its exhaust position until the exhaust cock is closed.The pressure in the working space(s) does not vary any longer and thepressure-sensitive element becomes stationary. However, thebypass-closing valve is not yet closed. Since in the case of an openedbypass the revolutions against torque curve of the engine is distortedin such manner that no stable point of intersection is to be found withthe revolutions against torque curve of the load, the danger exists thatin this situation the engine stops. In order to prevent this, an elementwhich is sensitive to the number of revolutions is present, which, whenthe number of revolutions falls below an adjusted zero-load number ofrevolutions, moves the second control device away from the second stopmember and hence in the first instance closes the bypass valve.

When a traction vehicle in which engine is disposed drives down a slope,the number of revolutions increases, the second control device willengage the second stop member; the bypass cock being opened. When thesupplied braking torque is too low, the inlet cock can be opened bymoving the first control device alone as result of which the pressurelevel in the engine increases and the braking torque also increases. Inthis manner it is possible to supply a large braking torque for a longperiod of time so that the working power of the vehicle can be fullyabsorbed by the engine.

In a favorable embodiment of the hot gas engine according to theinvention, the first control device comprises a first lever one endpivotally secured to the pressure-sensitive element and the other endcoupled in one direction of movement to a first operating device and inthe other direction of movement connected to a fixed part by means of aspring, which spring, in the case of nonenergized operating device,pulls the first lever against the first stop member. The second controldevice comprises a second lever having one end pivotally secured to thepressure-sensitive element and the other end coupled in one direction ofmovement to a second operating device and in the other direction ofmovement connected to a fixed part by means of a spring, which spring inthe case of nonenergized operating device, pulls the second leveragainst the second stop member. The first and the second stop membersare arranged so that upon displacement in the direction of the action ofthe spring the first lever contacts the first stop member sooner thanthe second lever contacts the second stop member; the second leverand/or the second operating device are arranged or provided with catchesso that upon displacement of the second lever against the action of thespring the first lever is also moved. In this manner an extremely simpleconstruction for controlling the position of the relative cocks isobtained, in which during normal operation both control devices cansimultaneously be displaced by means of the second operating device,while upon braking with the engine the first control device can be movedalone with the first operating device until the desired pressure levelin the working space(s) has adjusted; while in that case the secondlever remains engaging the second stop member due to the action of thespring thereby keeping the bypass cock maximally opened so that amaximum braking torque is supplied.

A further favorable embodiment of the hot gas engine according to theinvention includes the first control device which comprises a firstmovable liquid column having one end bounded by a piston cooperatingwith the inlet and exhaust cock and forced against the liquid column bythe action of a spring, and the other end bounded by a first movablepiston; the second control device comprises a second movable liquidcolumn having one end is bounded by a piston which cooperates with thebypass valve and is forced against the liquid column by the action of aspring and the other end bounded by a second movable piston. A firstoperating device is present with which the first movable piston can bemoved, as well as a second operating device being present with whichsimultaneously the first and the second movable piston can be moved; thefirst and second stop members are furthermore arranged so that themovement of the first movable piston in the direction of the action ofthe spring is smaller than that of the second movable piston, each ofthe two liquid columns being furthermore bounded by a further pistonwhich is connected to the pressure-sensitive element.

In order that the invention may be readily carried into effect, it willnow be described in greater detail, by way of example, with reference tothe accompanying drawings, in which FIG. 1 diagrammatically shows not toscale a monocylinder hot gas engine having a control device;

FIG. 2 diagrammatically shows a part of the control device of the hotgas engine shown in FIG. 1, in which an exhaust cock is provided in acommunication between the suction and compression duct of thecompressor;

FIG. 3 diagrammatically shows not to scale a four-cylinder hot gasengine having a control device;

FIG. 4 shows another embodiment of the control device shown in FIG. 2.

Reference numeral 1 in FIG. 1 denotes a cylinder in which a piston 2 anda displacer 3 reciprocate. The piston 2 and the displacer 3 areconnected by a piston rod 4 and a displacer rod 5, respectively, to agear not shown. Between the piston 2 and the displacer 3 there is acompression space 6 which communicates with an expansion space 10 via acooler 7, a regenerator 8 and a heater 9. Thermal energy can be appliedto the heater 9 by a burner 11. Below the piston 2 there is a bufferspace 12 which communicates, through a capillary duct 13, with thecompression space 6 so that in the buffer space 12 always the sameaverage pressure will adjust as in the compression space 6.

A medium supply duct 15 in which a nonreturn or one-way valve 16 isprovided which permits flow of medium in the direction of the workingspace communicates with the compression space 6. The medium supply duct15 furthermore comprises a controllable suppletion cock or inlet valve17. With its side remote from the compression space the medium supplyduct 15 communicates with a storage container 18 containing workingmedium.

A medium outlet duct 20 communicates with the compression space 6 andcomprises a nonreturn or one-way valve 21 which prevents flow of mediumin the direction of the compression space and furthermore comprises acontrollable exhaust cock or valve 22. With its side remote from thecompression space the medium outlet duct 20 communicates with the inlet23 of a compressor 24. The outlet 25 of the compressor 24 communicateswith the storage container 18 through a duct 26.

A communication duct 27v communicates with the compression space 6 andcomprises a controllable bypass cock or valve 28 which opens into thebuffer space 12 at its other end.

Two control devices of which the first comprises a lever 30 and thesecond comprises a lever 31 are present for operating the exhaust andinlet valves 22 and 17 and the bypass valve 28. Both levers arepivotally secured at their one end at 32 and 33 to a pressure-sensitiveelement 34 consisting of a piston 34 in a cylinder 35. The space 36 ofone side of the piston 34 communicates through a duct 37 with the bufferspace 12 so that in said bufi'er space the same average pressure willprevail as in the working space 6. A spring 38 is operative on the otherside of the piston 34.

The first lever 30 is coupled at one end through a transmission 39 to anoperating member 40 and at its other end it is coupled to a fixed partof the engine through a tension spring 41. A stop member 42 restrictsthe movement of the lever 30 in the direction of the action of thespring at its positive position. The second lever 31 is connected at itsone end through a transmission 43 to an operating member 44, and isconnected to a fixed part at its other end by a tension spring 45, themovement of the lever 31 in the direction of the action of the springbeing limited by a stop member 46 at its positive position. Thetransmission 43 comprises a catch 47 which is arranged so that when thelever 31 is parallel to the lever 30 the two levers are simultaneouslymovable by means of the operating device 44.

The operation of the hot gas engine is assumed to be known. The controlthereof occurs as follows. Starting or neutral position is the positionshown of the control device in which the inlet cock 17, the exhaust cock22 and the bypass cock 28 are all closed. When the coupling 43 is movedto the right to negative position by means of the operating member 44,the two levers 30 and 31 also move to the right and hence reach thenegative positions shown in broken lines I and II In this position ofthe levers the bypass cock 28 and the exhaust cock 22 remain closedwhile the suppletion cock 17 is opened. Medium from the storagecontainer 18 will now flow to the working space of the hot gas enginethrough the supply duct 15. As a result of this the average pressure inthe working space and in the buffer space 12 and hence also in the space36 of the pressure-sensitive element increases. This has for its resultthat the piston 34 is moved to the left or positive position against theaction of the spring 38. The pivots 32 and 33 of the levers also move tothe left so that the inlet cock 17 moves to its closed position, At theinstant the levers 30 and 31 have reached their neutral positions I andII" shown in dot and dash lines, the inlet cock 17 is again closed sothat the neutral position of the control device is then reached again inwhich a higher average pressure prevails in the working space and theengine will supply a larger torque. When the operating member 44 isreleased, the levers 30 and 31 move to the left or positive positionwhile opening both the exhaust cock 22 and the bypass cock 28. Byopening the exhaust cock 22, medium from the working space is drawn offvia outlet duct 22 to the compressor 24 and is then pumped back to thestorage container 18. As a result of this the average pressure in theworking space of the engine and hence the supplied power decrease.Furthermore, the bypass cock 28 is opened and due to flow lossesoccurring in said cock the phase between the volume and pressurevariations in the compression and expansion space varies so that a largepower reduction occurs. When the operating member 44 is entirelyreleased the levers 30 and 31 are pulled to positive position againstthe stop members 42 and 46 by springs 41 and 45, respectively. The stopmember 42 is arranged so that the lever 30 engages it sooner than lever31 engages stop member 46. The catch 47 is then released from the lever30. In this positive position of the levers 30 and 31 which is denotedby the broken lines 111' and IV, the exhaust cock 22 and the bypass cock28 are opened, Medium is conducted away from the working space via theexhaust cock 22 and the compressor 24 so that the pressure drops. Theresult of this is that the pressure in the space 36 also drops as thepiston 34 moves to the right under the influence of the spring 38. As aresult of this the ends 32 and 33 of the levers 30 and 31 also move tothe right. When the neutral position III of the lever 30, dot and dashlines has been reached, the exhaust cock 22 is closed again. The lever31 now takes a position IV" in which, however, the bypass cock 28 is notyet closed. A large braking torque is supplied by the maximally openedbypass cock which might have for its result that the engine cuts out. Inorder to prevent this a revolutions control 50 is present which, whenthe number of revolutions becomes smaller than the zero-load number ofrevolutions, moves the lever 31 away from the stop member 45 so that thebypass aperture becomes so much smaller that the zero-load number ofrevolutions remains maintained. I

When the number of revolutions of the engine increases, for example,because the vehicle in which the engine is arranged as a traction enginedrives down a hill, braking with the engine is possible by energizingthe operating pedal 40. With this operating pedal only lever 30 is movedto the right to negative position. This has for its result that thesuppletion cock 17 is opened and medium flows to the working space. As aresult of this the pressure rises. As a result of this rise in pressurethe piston 34 moves to the left as a result of which the ends 32 and 33of the levers 30 and 31 also move to the left. As a result of this theinlet cock 17 closes and the bypass cock 28 is further opened. Thebypass cock 28 is constructed so that in the case of maximum pressure inthe working space the aperture of the bypass cock 28 is such that theengine supplies a maximum braking torque.

In this manner it is thus possible to adapt during normal operation thetorque supplied by the engine to the required torque by means of oneoperating device 44, while the engine can supply a braking torque bymeans of a second operating device 40 so that working power of movementcan .be converted via the engine into thermal energy which can beconducted away with the cooling water in the cooler 7.

In FIG. 2 the exhaust cock 22 is directly provided in the medium outletduct 20. Without altering the control device the outlet of medium canalso be controlled by an exhaust cock 22 which is arranged in acommunication 'duct 51 between the medium outlet duct 20 and the duct26. The only difference is that in the open condition of the exhaustcock 22' no removal of medium out of the working space takes place butthat removal takes place only when the exhaust cock 22' is closed, Theoperation of the control is entirely similar to that shown in FIG. 1 sothat further description thereof may be omitted.

FIG. 3 shows a hot gas engine having four cylinders 55, 56, 57 and 58.Each of these cylinders communicates, through nonreturn valves 59, 60,61 and 62 which permit flow of medium in the direction of the relativecylinder, with a medium supply duct 63. Each of these cylinderscommunicates further via nonreturn valves 64, 65, 66 and 67 whichprevent flow of medium towards these cylinders, with a medium outletduct 68. The medium supply duct 63 comprises a controllable inlet cock17 and communicates at its other end with a storage container 18. Themedium outlet duct 68 communicates with its other end with the inlet 23of a compressor 24, the outlet 25 of which communicates with the storagecontainer 18 via a duct 26 with a nonreturn valve 70 incorporatedtherein. Between the medium outlet duct 68 and the duct 26 acommunication duct 50 is present in which an exhaust cock 22 isprovided.

The bypass cock 28 is arranged in the communication duct 71 between themedium outlet duct 68 and medium supply duct 63.

The control device corresponds to that shown in F IG. 1 with thedifference that in this embodiment the levers 30 and 31 pivot about thesame pivot 72 which is again connected to the piston 34 of apressure-sensitive element. The space 36 on one side of the piston 34communicates with the medium outlet duct 68. Since the medium outletduct 68 communicates with the cylinders via nonreturn valves 64, 65, 66and 67 which permit flow in the direction of the duct 68, the maximumpressure which occurs in the working spaces will prevail in the outletduct 68.

By energizing the operating member 44, both levers 30 and 31 will moveto the left, the inlet cock 17 being opened. Although the exhaust cock22' is also opened, this has for its result that the suction andcompression side of the compressor 24 are inopen communication with eachother so that the compressor causes no transport of medium and hence noremoval of working medium takes place to the storage contamer.

Medium flows to the working spaces 55, 56, 57 and 58 through the openinlet cock 17, As a result of this the pressure level in said workingspaces and hence also the maximum pressure increases. The pressure inthe medium outlet duct 68 and in the space 36 will consequently alsoincrease. As a result of this the piston 34 and consequently also thelevers 30 and 31 move to the right so that the inlet cock 17 moves toits closed position.

When the operating member 44 is released, the levers 30 and 31 move tothe right so that the exhaust cock 22 closes and the bypass cock 28opens. As a result of the closure of the cock 22, the medium sucked by'the compressor 24 will be conducted away to the storage container 18 sothat removal of working medium from the working spaces takes place andthe pressure level therein drops. This has for its result that thepressure in the space 36 also drops and the piston 34 moves to the leftso that the levers 30 and 31 also experience a movement to the left andthe cock 22' opens again and the cock 28 closes. When the cock 28 isopened, a flow of medium takes place from the outlet duct 68 to thesupply duct 63 and then via the working spaces again to the outlet duct68. Due to this circulation of medium a reduction occurs of the powersupplied by the engine.

When the operating device 44 is entirely released, the levers 30 and 31are pulled against their stop members 42 and 46 by the springs 41 and45, the lever 30 again contacting the stop member 42 sooner than thelever 31 contacts the stop member 45. This again has for its result asin FIG. 1 that the exhaust cock 22' will again reach its nonexhaustposition (closed position) before the bypass cock 28 is opened. In orderto prevent the engine from cutting out, in this situation, a revolutioncontrol 50 is present again as in FIG. 1; when the number of revolutionspasses below the zero-load number of revolutions the control 50 movesthe lever away from the stop member 46 so that the bypass aperture isthen reduced.

Referring again to FIG. 1, in order to cause the engine to supply alarge barking torque, the operating member 40 may be energized again asa result of which the lever 30 alone moves to the right and the inletcock 17 opens. As a result of this the pressure level in the enginerises. The piston 34 moves to the right as a result of the increasedpressure and the bypass cock 28 reaches its maximally open position sothat a maximum braking torque is supplied. So in this manner a hot gasengine is obtained having a mountain brake.

Although the control device in the hot gas engines shown in the abovefigures is constructed with levers, it will be obvious that otherconstructions are also possible. In FIG. 4 the control device used inthe engine shown in FIG. 3 is constructed with movable liquid columns130 and 131 instead of movable levers. On one side the liquid column 130is bounded by a piston 133 which is forced against the liquid by aspring 134 and the piston rod 135 which cooperates with the exhaust cock22 and suppletion cock 17. The liquid column 131 is bounded on its oneside by a piston 136 which is forced against the liquid by a spring 137and the piston rod 138 of which is connected to a bypass cock 28. At itsother end the liquid column 130 is bounded by a piston 140 having apiston rod 141 which comprises studs 142 and 143, while the liquidcolumn 131 is bounded on its other side by a piston 144 having a pistonrod 145 which comprises studs 146 and 147.

Furthermore a first operating device 148 is present which cooperateswith stud 142 while a second operating device 149 cooperates with stud143 which is connected to the piston 140 and with stud 146 which isconnected to piston 144. Further more an element 150 which is sensitiveto the number of revolutions is present which when the number ofrevolutions fall below the zero-load number of revolutions, cancooperate with stud 147 which is connected to the piston 144. Stopmembers 151 and 152 limit the movement of the pistons 140 and 144 in thedirection of the action of the springs 134 and 137, respectively. Theliquid columns 130 and 131 are furthermore bounded by pistons 153 and154 the piston rods 155 and 156 of which are each connected to a piston34 of a pressure-sensitive element as described in the precedingfigures.

By energizing the operating device 14% the pistons 140 and 144 are bothmoved downwards. The result of this is that the pistons 133 and 136 alsomove downwards. The exhaust cock 22' remains in its nonexhaust position(open) and the inlet cock 17 remains open while the bypass member 28closes the communication duct 171. Due to the suppletion of workingmedium the pressure level in the working space increases and also thepressure in the spaces 36 increases so that the pistons 34 move againstthe action of the spring 38. As a result of this the pistons 153 and 154move outwards so that as it were a shortening of the liquid columns 130and 131 occurs so that the pistons 133 and 136 return to their initialposition, closing the inlet cock 17.

When the operating device 149 is entirely released the pistons 140133and 144-136 move upwards until the piston rods 141 and 145 engage thestop members 151 and 152. The exhaust cock 22' is then closed so thatremoval of working medium from the working spaces takes place and bypassmember 28 is then maximally open. By the removal of medium the pressurein the working spaces drops and hence also in the spaces 36 so that thepistons 34 move inwards under the influence of the springs 38 thereby,as it were, causing an elongation of the liquid column so that thepistons 133 and 136 move downwards. This is continued until the exhaustcock 22' is opened again. The bypass member 28 will not yet assume itsclosed position. If in this situation the number of revolutions fallsbelow the zero-load number. of revolutions, the element 150 which issensitive to the number of revolutions will contact stud 47 and forcesaid stud downwards so that the bypass member 28 will consequently beclosed further.

In order to obtain a large braking torque, the operating member 148 isenergized so that the piston 140 alone is moved downwards and the inletcock 17 is opened so that suppletion of medium takes place and thepressure level increases. As a result of this the pressure in the spaces36 will also increase so that the pistons 153 and 154 move outwards as aresult of which as it were again a shortening of the liquid columns and131 occurs and the pistons 133 and 136 move upwards, thereby againclosing the inlet cock 17 and further opening the bypass member 28. Theengine then supplies a maximum braking torque.

What is claimed is:

1. In a hot gas engine operable witha source of fluid medium, andincluding at least one working space, one buffer space, an inlet ductfor flowing medium from the source to the working space, and an outletduct for discharging medium from the working space, the improvement of acontrol device in combination therewith comprising:

a. a one-way valve in each of said inlet and outlet ducts,

b. an adjustable inlet valve in the inlet duct, and an adjustableexhaust valve in the outlet duct, both valves spring biased in closedposition,

. a capillary duct for communicating between and maintaining the sameaverage pressure in the working and buffer spaces,

d. a communication duct including an adjustable bypass valve springbiased in closed position connecting the working space with the bufferspace,

first spring-biased control means movable between (i) neutral positionwhereby the inlet and exhaust valves are closed, (ii) positive positionwhereby the inlet valve is open and the exhaust valve is closed, and(iii) negative position whereby the exhaust valve is open and the inletvalve is closed,

second spring-biased control means movable between (1) neutral positionwhereby the bypass valve is closed, and (ii) positive position wherebythe bypass valve is open,

g. Third means which engages the first and second means, is incommunication with the working space, and is movable between positive,neutral and negative positions in response to increased and reducedpressure respectively in the working space, movement of the third meanstoward positive and negative positions respectively urging the first andsecond means toward their corresponding positive and negative positions,

h. a fourth means, engaged to the second means and responsive to engineoutput speed below zero-load, for moving the second means to effectclosure of the bypass valve, and

i. fifth means connecting the first and second means whereby movement ofthe second means between its positions causes corresponding movement ofthe first means.

2. Apparatus according to claim 1 comprising stop means for insuring,when the second means is moved to its positive position, it reaches saidposition before the first means reaches its positive position.

3. Apparatus according to claim 2 wherein the stop means comprises firstand second stop elements for arresting motion of the first and secondmeans when they are moved to their positive positions.

4. Apparatus according to claim 1 wherein the fourth means is acentrifugal governor device.

5. Apparatus according to claim 1 wherein the first and second means arelevers movable about their respective pivot points, and said third meansengages and moves said pivot points to displace the levers to locationscorresponding to different positions.

6. Apparatus according to claim 1 wherein said first and second controlmeans are mechanical linkages, each having one part manually operableand a separate part engaged to the associated valve.

7. Apparatus according to claim 1 wherein said first and second controlmeans are fluid linkages comprising containers of movable fluid, eachcontainer including one piston engaging the fluid for initiating actionthereof, and a second remote piston driven by the fluid for actuatingthe associated valve.

8. Apparatus according to claim 1 in combination with a plurality ofsimilar hot gas engine working spaces.

9. In a hot gas engine operable with a source of fluid medium, andincluding one working space, one buffer space, a bypass duct and valveconnecting the working and buffer spaces, an inlet duct for flowingmedium from the source to the working space, and an outlet duct fordischarging medium from the working space, the improvement comprising ofa control device in combination therewith,

a. first means for increasing power output of the engine from a neutralcondition by providing additional medium to the working space andthereby operating at a higher pressure, and for decreasing power byremoving medium to operate at a lower pressure,

b. second means for providing braking torque from the engine, by shortcircuiting the working and buffer spaces formed by openable bypass ductmeans therebetween,

c. third means for sensing low engine speed and increasing power toprevent engine stalling by closing said second means duct, and

fourth means for sensing pressure change in the working space andsubsequently returning the first and second means to a neutralcondition.

10. Apparatus according to claim 9 wherein said first means comprises aninlet valve for permitting medium flow from the source to the workingspace, and an exhaust valve for permitting discharge of medium from theworking space, and a linkage for selectively opening and closing saidinlet and outlet valves.

11. Apparatus according to claim 10 wherein said second means comprisesa linkage for selectively opening and closing said bypass duct.

1. In a hot gas engine operable with a source of fluid medium, andincluding at least one working space, one buffer space, an inlet ductfor flowing medium from the source to the working space, and an outletduct for discharging medium from the working space, the improvement of acontrol device in combination therewith comprising: a. a one-way valvein each of said inlet and outlet ducts, b. an adjustable inlet valve inthe inlet duct, and an adjustable exhaust valve in the outlet duct, bothvalves spring biased in closed position, c. a capillary duct forcommunicating between and maintaining the same average pressure in theworking and buffer spaces, d. a communication duct including anadjustable bypass valve spring biased in closed position connecting theworking space with the buffer space, e. first spring-biased controlmeans movable between (i) neutral position whereby the inlet and exhaustvalves are closed, (ii) positive position whereby the inlet valve isopen and the exhaust valve is closed, and (iii) negative positionwhereby the exhaust valve is open and the inlet valve is closed, f.second spring-biased control means movable between (1) neutral positionwhereby the bypass valve is closed, and (ii) positive position wherebythe bypass valve is open, g. Third means which engages the first andsecond means, is in communication with the working space, and is movablebetween positive, neutral and negative positions in response toincreased and reduced pressure respectively in the working space,movement of the third means toward positive and negative positionsrespectively urging the first and second means toward theircorresponding positive and negative positions, h. a fourth means,engaged to the second means and responsive to engine output speed belowzero-load, for moving the second means to effect closure of the bypassvalve, and i. fifth means connecting the first and second means wherebymovement of the second means between its positions causes correspondingmovement of the first means.
 2. Apparatus according to claim 1comprising stop means for insuring, when the second means is moved toits positive position, it reaches said position before the first meansreaches its positive position.
 3. Apparatus according to claim 2 whereinthe stop means comprises first and second stop elements for arrestingmotion of the first and second means when they are moved to theirpositive positions.
 4. Apparatus according to claim 1 wherein the fourthmeans is a centrifugal governor device.
 5. Apparatus according to claim1 wherein the first and second means are levers movable about theirrespective pivot points, and said third means engages and moves saidpivot points to displace the levers to locations corresponding todifferent positions.
 6. Apparatus according to claim 1 wherein saidfirst and second control means are mechanical linkages, each having onepart manually operable and a separate part engaged to the associatedvalve.
 7. Apparatus according to claim 1 wherein said first and secondcontrol means are fluid linkages comprising containers of movable fluid,each container includIng one piston engaging the fluid for initiatingaction thereof, and a second remote piston driven by the fluid foractuating the associated valve.
 8. Apparatus according to claim 1 incombination with a plurality of similar hot gas engine working spaces.9. In a hot gas engine operable with a source of fluid medium, andincluding one working space, one buffer space, a bypass duct and valveconnecting the working and buffer spaces, an inlet duct for flowingmedium from the source to the working space, and an outlet duct fordischarging medium from the working space, the improvement comprising ofa control device in combination therewith, a. first means for increasingpower output of the engine from a neutral condition by providingadditional medium to the working space and thereby operating at a higherpressure, and for decreasing power by removing medium to operate at alower pressure, b. second means for providing braking torque from theengine, by short circuiting the working and buffer spaces formed byopenable bypass duct means therebetween, c. third means for sensing lowengine speed and increasing power to prevent engine stalling by closingsaid second means duct, and fourth means for sensing pressure change inthe working space and subsequently returning the first and second meansto a neutral condition.
 10. Apparatus according to claim 9 wherein saidfirst means comprises an inlet valve for permitting medium flow from thesource to the working space, and an exhaust valve for permittingdischarge of medium from the working space, and a linkage forselectively opening and closing said inlet and outlet valves. 11.Apparatus according to claim 10 wherein said second means comprises alinkage for selectively opening and closing said bypass duct.